Dissociation of water on rhodium nanoclusters supported by graphene grown on Ru(0001)

Yi-Cheng Huang^1*, Yu-Yao Hsia¹, Alfiatur Rahmah¹, Yu-Ling Lai², Yao-Jane Hsu², Meng-Fan Luo¹

¹Department of Physics, National Central University, Taoyuan, Taiwan
²National Synchrotron Radiation Research Center, Hsinchu, Taiwan

* Presenter:Yi-Cheng Huang, email:hi820410@gmail.com

The dissociation of water on clean and oxygen-precovered rhodium (Rh) nanoclusters supported on graphene grown on Ru(0001) single crystal was studied, under ultrahigh vacuum conditions and using scanning tunneling microscopy (STM), reflection high-energy electron diffraction (RHEED), synchrotron-based photoemission (PES). The graphene film was grown with thermal decomposition of ethylene on Ru(0001) at 950 K and Rh clusters on depositing vapors of Rh onto graphene/Ru(0001) at 300 K. We compared the water reaction on the supported Rh clusters to that on Rh(111) single crystal in the present report. The results show that water adsorbed molecularly on both surface; no water was dissociated and water desorbed below 200 K. In contrast, on atomic oxygen (O*) pre-covered Rh clusters or Rh(111), a great fraction of water molecules underwent dissociation into atomic hydrogen and hydroxyl groups. On Rh(111) surface, the effect was significant at a small O* coverage and attenuated with increased O*, while on Rh clusters, the effect persisted for any O* coverage. On 1.0 ML Rh clusters, the hydroxyl group increased with O*; in contrast, on 4.0 ML Rh clusters, the hydroxyl group decreased with increased O* coverage.

Keywords: Water dissociation, Oxygen, Rh(111), Rhodium nanocluster